Thousands of patients, including many children, become blind from retinitis pigmentosa and allied diseases. At present no treatments are known for practically all types. Full-field electroretinographic (ERG) testing has provided criteria for early diagnosis. Not only reductions in amplitude but also delays in cone and rod ERG b-wave implicit times have been recorded in different genetic types. Research will include simulation in normal subjects of the abnormal cone and rod ERGs recorded from patients with retinitis pigmentosa and allied diseases to arrive at pathophysiological mechanisms that could explain the waveforms seen in disease. Pharmacologic studies of drugs with known mechanisms of action on cells will be evaluated with respect to their effects on retinal function in cats to try to simulate the ERG waveforms in different types of human hereditary disease and to produce acute models for retinitis pigmentosa and allied diseases. Dogs with an autosomal recessive form of hereditary retinal degeneration will be studied with the early receptor potential (ERP) and the ERG c-wave at different states of retinal degeneration; responses from dogs will be compared with those obtained from patients with hereditary retinal disease. Mice with known non-retinal X-linked mutations will be studied with electroretinography to seek models of human sex-linked retinal disease. Possible effects of traction on the retina due to a preretinal membrane in the macula of patients with retinitis pigmentosa and allied diseases will be evaluated in the ERG by monitoring the Stiles-Crawford effect; this study will be done to see if abnormal photoreceptor orientation occurs in patients who have slight reductions in visual acuity with abnormal wrinkling or high retinal reflexes seen in the macula with an ophthalmoscope.